Highly fluorescent markers for fluids or articles

ABSTRACT

The present invention provides highly fluorescent markers, made from a reactive polymer and an isocyanate, that fluoresce in the ultraviolet or near infrared region without being visible to the human eye at low concentrations in the fluid or article being marked. The molecular weight and fluorescence emission wavelength of these highly fluorescent marker compounds can be adjusted to provide a multitude of markers with unique fluorescence signatures.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of copending U.S.application Ser. No. 10/971,825, filed on Oct. 22, 2004.

FIELD OF THE INVENTION

The present invention relates, in general, to fluorescent markermolecules and, more specifically, to the preparation of highlyfluorescent polyurethane compounds which are the reaction products of anisocyanate with fluorescent or non-fluorescent reactive polymers. Thesehighly fluorescent polyurethane compounds provide unique markers foridentifying the sources of component raw materials in fluids, fluidblends and solid compositions.

BACKGROUND OF THE INVENTION

Various colorants and dyes have been used to authenticate thecomposition and/or source of fluids and plastic articles. In some cases,it is preferable to use a marker or tag that is not detectable by thehuman eye so as to avoid interference with colored materials or to avoiddetection of the additive. In such cases, it may be desirable to usemarker compounds containing fluorophores that fluoresce or emit light inthe ultraviolet or infrared region after excitation with an appropriatelight source. For instance, U.S. Pat. Nos. 4,303,701 and 4,329,378disclose methods for marking plastic lenses by impregnating them withfluorescent materials that do not respond to sunlight or normal visiblelight.

Luttermann et al., in U.S. Pat. No. 5,201,921 teach a process foridentifying polyolefin plastics using lipophilic fluorescent dyes inconcentrations suitable to minimize color distortions.

Markers are also becoming particularly important for protecting brandintegrity for consumers. Such markers must be readily detectable atrelatively low concentrations in the product. In the petroleum industry,markers are also useful for ensuring compliance with governmentalregulations. For example, products such as diesel fuels, gasoline andheating oils often contain visible dyes or colorless fluorescentcompounds that identify the intended use, tax status, or brand name ofthe product. Such markers are well known to those skilled in the art.

In addition, petroleum product markers must also fulfill other criteriasuch as being:

-   -   (1) soluble in hydrocarbon solvents;    -   (2) resistant to leaching from the petroleum product by water or        water that is strongly acidic or basic;    -   (3) relatively chemically inert so as to avoid loss of color or        fluorescence when in contact with other petroleum additives or        water; and    -   (4) free from interference from naturally occurring compounds        already present in the petroleum product.

A number of artisans have attempted to provide acceptable fluorescentmarkers for use in the petroleum industry. For example, Smith, in U.S.Pat. No. 5,498,808, teaches the use of colorless fluorescent petroleummarkers which are based on esterified derivatives of xanthene compoundssuch as fluorescein. One drawback to the markers of Smith is that fuelscontaining these markers must be treated with alkaline developingsolutions to generate the visibly fluorescent chromophore. Other markerssuch as the phthalocyanine and naphthalocyanine dyes, disclosed in U.S.Pat. Nos. 5,804,447, 5,998,211 and 6,312,958, can be detected directlyby their fluorescence in the near infrared (IR) region between 600 to1,200 nm where naturally occurring components in the petroleum productwill not interfere.

Carbamates or urethanes prepared with aromatic isocyanates are known tofluoresce in the ultraviolet region between 300 and 400 nm dependingupon the substitution pattern of the isocyanate, solvent, and thealcohol used. Because petroleum compounds typically exhibit considerablebackground fluorescence at these wavelengths, urethanes have heretoforetended to be excluded from consideration as markers.

U.S. Pat. Nos. 3,844,965 and 4,897,087 disclose lubricating oiladditives and ash less fuel detergents or dispersants which are said tobe the reaction products of a polyether polyol and an aliphatichydrocarbyl amine or polyamine with a polyisocyanate (i.e., polyetherurethaneureas). Polyether urethane polyamines prepared fromhydroxyalkylated polyamines, a polyisocyanate, and a polyether can beused as fuel additives with enhanced oxidative stability as taught byBlain et al. in U.S. Pat. No. 5,057,122. However no mention is made inany of these patents about the use of these compounds as fluorescentmarkers and no methods of enhancing their fluorescent response isdiscussed.

Polyether polyurethanes without active hydrogens have been used asplasticizers in U.S. Pat. Nos. 4,824,888, 5,525,654, and 6,403,702.These compounds are essentially diurethanes prepared by:

-   -   1) reaction of difunctional polypropylene glycol with a        monoisocyanate or    -   2) reaction of a monofunctional monalkyl ether of polypropylene        glycol with a diisocyanate.

Pantone et al., in U.S. Pat. No. 6,384,130, disclose another class ofplasticizers that are the reaction products of an isocyanate-terminatedprepolymer and a monofunctional alcohol. These compounds contain morethan two urethane groups and the prepolymers may have a functionalitygreater than 2.0. The polyethers disclosed by Pantone et al. to make thepolyurethanes do not contain fluorophores.

Reactive dyestuffs or colorants for plastics based on alkoxylatedchromophores such as azo, triphenylmethane, and anthraquinonederivatives are disclosed in U.S. Pat. Nos. 4,284,729 and 4,846,846. Thepolyether derivatives provide non-migrating visible color topolyurethane articles by chemically reacting with isocyanates in theblend to become part of the polymer network. Again, no mention is madein any of these patents about the use of these compounds as fluorescentmarkers and no methods of enhancing or controlling their fluorescentresponse is discussed.

Thus, a need continues to exist in the art for colorless markers. Itwould be desirable if such markers had molecular structures that can bereadily modified to provide fluorescence in the ultraviolet, visible, ornear infrared (IR) region of the electromagnetic spectrum.

SUMMARY OF THE INVENTION

The present invention provides such markers in the form of highlyfluorescent polymeric urethane or urea derivatives that fluoresce in theultraviolet or near infrared region without being visible to the humaneye at low concentrations in the fluid or article being marked. Thesehighly fluorescent markers can be detected by techniques such as liquidor gel permeation chromatography coupled with appropriate detectors. Themarker compounds are compatible with an extensive variety of materials,including petroleum products. The molecular weight and fluorescenceemission wavelength of the compounds can be readily adjusted to providea multitude of markers having unique fluorescence signatures. Inaddition, because the marker compounds are highly fluorescent, less ofthe particular compound is needed to provide an identifying signal.

These and other advantages and benefits of the present invention will beapparent from the Detailed Description of the Invention herein below.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described for purposes of illustrationand not limitation. Except in the operating examples, or where otherwiseindicated, all numbers expressing quantities, percentages,functionalities and so forth in the specification are to be understoodas being modified in all instances by the term “about”. Equivalentweights and molecular weights given herein in Daltons (Da) are numberaverage equivalent weights and number average molecular weightsrespectively, unless indicated otherwise.

The present invention provides a highly fluorescent compound containingthe reaction product of at least one fluorophore-containing reactivepolymer, optionally containing a polyamine unit of the formula NCH₂CH₂Nand at least one unsubstituted or substituted aryl isocyanate or anunsubstituted or substituted aliphatic or cycloaliphatic isocyanate, atan isocyanate index of 100 or less, wherein the highly fluorescentcompound emits fluorescence in the ultraviolet (UV), visible, or nearinfrared (IR) region.

The present invention further provides a process for producing a highlyfluorescent compound involving reacting at least onefluorophore-containing reactive polymer, optionally containing apolyamine unit of the formula NCH₂CH₂N and at least one unsubstituted orsubstituted aryl isocyanate or an unsubstituted or substituted aliphaticor cycloaliphatic isocyanate, at an isocyanate index of 100 or less,wherein the highly fluorescent compound emits fluorescence in theultraviolet (UV), visible, or near infrared (IR) region.

The present invention still further provides a process for marking oneof a fluid, a fluid blend or a solid composition, involving adding tothe one of a fluid, a fluid blend or a solid, the reaction product of atleast one fluorophore-containing reactive polymer, optionally containinga polyamine unit of the formula NCH₂CH₂N and at least one unsubstitutedor substituted aryl isocyanate or an unsubstituted or substitutedaliphatic or cycloaliphatic isocyanate, at an isocyanate index of 100 orless, wherein the reaction product emits fluorescence in the ultraviolet(UV), visible, or near infrared (IR) region.

The present invention yet further provides a process for marking one ofa fluid, a fluid blend or a solid composition, involving adding to theone of a fluid, a fluid blend or a solid, the reaction product of atleast one non-fluorophore-containing reactive polymer, optionallycontaining a polyamine unit of the formula NCH₂CH₂N and at least oneunsubstituted or substituted aryl isocyanate, at an isocyanate index of100 or less, wherein the reaction product emits fluorescence in theultraviolet (UV), visible, or near infrared (IR) region.

The highly fluorescent inventive polymeric urethane or urea derivativesfall into two classes depending upon the fluorescence characteristics ofthe active hydrogen compound and the type of isocyanate used.

-   Class I. The reaction product of a reactive polymer containing a    fluorescent chromophore and an aromatic isocyanate, represented by    the formula (I) below:

-   -   wherein    -   F represents a fluorophore;    -   P represents a polymeric moiety, optionally containing a        polyamine unit of the formula NCH₂CH₂N;    -   X represents a reactive heteroatom chosen from O, N, and S;    -   n represents the number of reactive heteroatoms;    -   R¹ represents an unsubstituted or substituted aryl moiety; and    -   y represents the number of isocyanate groups.

-   Class II. The reaction product of a reactive polymer containing a    fluorescent chromophore and an aliphatic or cycloaliphatic    isocyanate, represented by the formula (II) below:

-   -   wherein,    -   F represents a fluorophore;    -   P represents a polymeric moiety, optionally containing a        polyamine unit of the formula NCH₂CH₂N;    -   X represents a reactive heteroatom chosen from 0, N, and S;    -   n represents the number of reactive heteroatoms;    -   R² represents an unsubstituted or substituted aliphatic or        cycloaliphatic moiety; and    -   y represents the number of isocyanate groups.

Also suitable as markers in the inventive methods are those polymericurethane or urea derivatives which do not contain a fluorophore, but docontain an aromatic group in the isocyanate moiety, and are hereindesignated as Class III compounds.

-   Class III. The reaction product of a reactive polymer not containing    a fluorescent chromophore and an aromatic isocyanate, represented by    the formula (III) below:

-   -   wherein,    -   P represents a non-fluorophore-containing polymeric moiety,        optionally containing a polyamine unit of the formula NCH₂CH₂N;    -   X represents a reactive heteroatom chosen from 0, N, and S;    -   n represents the number of reactive heteroatoms;    -   R³ represents an unsubstituted or substituted aryl moiety; and        represents the number of isocyanate groups.    -   y represents the number of isocyanate groups.

The highly fluorescent marker compounds of these three classespreferably have a molecular weight greater than 300 Da, more preferablybetween 1,000 and 50,000. The excitation wavelength to inducefluorescence is preferably greater than 210 nm and the emissionwavelength is preferably greater than 290 nm. Surprisingly, the relativefluorescence of the marker compounds is greater than that expected fromthe simple addition of the fluorescence of the reactant fluorophoresand, in some cases, may be up to seven times as much as expected. Thisallows for the use of greatly reduced amounts of the compounds asmarkers.

It is preferred that neither the reactive polymer nor the isocyanateabsorb light in the visible region to the extent that any significantcolor is observed, but the reaction product may fluoresce in theultraviolet below 400 nm, in the visible region, or in the near infraredabove 700 nm. The highly fluorescent marker compounds are not intendedto become chemically bound to the matrix in which they are used.

The chemical composition of the reactive polymer is not critical, butthe reactive polymer should be soluble in the matrix in which it is tobe used. Although polyesters are suitable, polyethers based on alkyleneoxides or combinations of alkylene oxides such as ethylene oxide,propylene oxide, or butylenes oxide are preferred. The molecular weightof the reactive polymer should be such that the fluorescence intensityof its reaction product with an isocyanate allows detection of thecompound at concentrations below 100 ppm. Preferably, the reactivepolymer has a molecular weight in the range of 250 to 40,000 Da, morepreferably in the range of 500 to 20,000 Da. Additionally, thefunctionality or number of active hydrogen atoms per molecule ofreactive polymer may vary from 1 to 8. The chain length of the reactivepolymer and the fluorophore may be chosen to adjust respectively thechromatographic behavior and fluorescent emission wavelength for thecompound as desired. Reactive heteroatoms as used herein refers tooxygen, nitrogen or sulfur atoms of the reactive polymer which hadreactive hydrogen atoms prior to reaction with the isocyanate in formingthe highly fluorescent compound.

Fluorophores and methods of making them are known in the art. Thefluorophore may be attached to the reactive polymer via any type oflinking group such as an ester, amide, ether, etc., by means known tothose skilled in the art.

In the case of the inventive Class I or the Class III compounds, thearomatic isocyanate may be mono or polyfunctional depending upon thedesired molecular architecture of the reaction product. Suitableisocyanates include, but are not limited to, 4,4′-diphenylmethanediisocyanate (MOO, polymeric MOI (PMDI), toluene diisocyanate,allophanate-modified isocyanates, phenyl isocyanate, naphthaleneisocyanate, naphthalene diisocyanate, isocyanate-terminated prepolymersand carbodiimide-modified isocyanates.

In the case of the inventive Class II compounds, suitable aliphatic orcycloaliphatic isocyanates include, but are not limited to,1,6-hexamethylene-diisocyanate; isophorone diisocyanate; 2,4- and2,6-hexahydrotoluenediisocyanate, as well as the corresponding isomericmixtures; 4,4′-, 2,2′- and 2,4′-dicyclohexylmethanediisocyanate and 1,3tetramethylene xylene diisocyanate.

As will be apparent to those skilled in the art, the inventive markercompounds may be made including various combinations of reactivepolymers and isocyanates.

For the inventive marking methods, it is preferred that the highlyfluorescent marker compounds be liquid and readily soluble in fluids.Therefore, those conditions which would produce high crosslink densityor insoluble solids are preferably avoided, i.e., where n, in formulae(I), (II) or (III) is greater than one, a monofunctional isocyanate ispreferred and where y is greater than one, a monofunctional polymer ispreferred. If use of a diisocyanate is desired for n>1, a mixture ofmono- and difunctional polymeric group is preferably used to control themolecular weight of the polyurethane product. The isocyanate index forreaction of the polymer with the isocyanate is less than or equal to 100but a value of 100 is preferred.

The term “Isocyanate Index” (also commonly referred to as NCO index), isdefined herein as the number of equivalents of isocyanate, divided bythe total number of equivalents of isocyanate-reactive hydrogencontaining materials, multiplied by 100, (i.e., NCO/(OH+NH)×100).

The fluorescence signature of the marker compounds may be adjusted byvarying the chain length of the polymeric group, the presence or absenceof fluorophore and the type of fluorophore. The highly fluorescentmarker compounds may be added to the matrix to be marked in any amountdepending upon the sensitivity of the detection system. The inventorherein contemplates that, with present technologies, detection may beeffected at amounts of at least one part of the inventive compound perbillion parts of matrix up to perhaps 100 parts per million. The matrixto be marked is virtually unlimited. Fluids, fluid blends and solidcompositions (preferably before solidification has occurred) may bemarked with the inventive compounds. The highly fluorescent markercompounds may be used to mark fluid blends, such as petroleum productsincluding diesel fuel, gasoline and heating oil. Although less preferredbecause of a weaker signal, the inventor herein also contemplates theuse of a fluorophore-containing polymer itself in the inventive markingmethods.

EXAMPLES

The present invention is further illustrated, but is not to be limited,by the following examples.

Highly Fluorescent Marker Preparation Procedure

An apparatus was assembled from a three-liter resin kettle with afour-necked glass cover. A metal stirrer shaft with three Rushtonturbines was inserted into the central neck. The other necks were fittedwith a thermocouple, a nitrogen line, and a vacuum line. The resinkettle was inserted into a heating mantle jacket. The assembly wasflushed with nitrogen for 15 minutes before charging 2,370 grams (1.483equivalents) of polyether polyol to the resin kettle. The polyether wasvacuum-stripped at 20-25 mm Hg while heating to 110° C. for two hours.The polyol was cooled to 60° C. before sufficient isocyanate was addedto achieve the desired index. The mixture was heated for two to fourhours at 125° C. under a nitrogen blanket. Consumption of the isocyanatewas monitored by standard titration methods. The isocyanate index wasvaried from 90 to 100 and the amount of each reactant was dependent uponits active hydrogen content.

Fluorescence Analysis Method

High Performance Liquid Chromatography (HPLC) analyses of the highlyfluorescent marker compounds were performed using a Model 1090M HPLC(Agilent Technologies) equipped with a Model 1046A Fluorescencedetector. A five microliter aliquot of a 100 ppm solution of each markercompound was injected into the HPLC, which contained no analyticalcolumn and used unstabilized THF as mobile phase at a flow rate of 0.5milliliters per minute. Because no analytical column was used, allcomponents of each sample were unretained by the system and elutedtogether.

The fluorescent responses were monitored primarily at three specifiedwavelength combinations, namely: Excitation at 240 nm/Emission at 325nm; Excitation at 240 nm/Emission at 310 nm; and Excitation at 230nm/Emission at 310 nm. The photomultiplier tube (PMT) sensitivity wasset at 8. Comparisons of marker compounds responses were based on peakarea data.

Peak areas for the emission spectra of the marker compounds werecompared to the peak area for a control to obtain the relative responseratio. The control was a polyether prepared by propoxylatingnonylphenol. Although there was little difference in the response ratioswhen the excitation wavelength was 230 nm, various combinations ofpolymer fluorophores and aromatic isocyanates enhanced responses fromtwo to nine times when excitation at 240 nm was used.

Table I details the composition of the highly fluorescent markercompounds and summarizes the results of fluorescence measurementsperformed at various combinations of excitation and emissionwavelengths. The molecular weights listed correspond to the unreactedpolymer.

TABLE I Fluorescence in THF Highly Fluorescent Marker CompoundExcitation 230 nm Excitation 240 nm Excitation 240 nm Reactive PolymerIsocyanate Emission 310 nm Emission 310 nm Emission 325 nm Ex. No.Fluorophore Funct. MW Funct. Area Ratio Area Ratio Area Ratio C-1nonylphenol 1 1,600 none — 592 1.0 108 1.0 54 1.0 2 nonylphenol 1 1,6004,4′-MDI 2 856 1.4 721 6.7 476 8.8 3 nonylphenol 1 1,600 phenylisocyanate 1 789 1.3 211 2.0 105 1.9 4 Bisphenol A 2 3,000 phenylisocyanate 1 1,023 1.7 344 3.2 185 3.4 5 Bisphenol A 2 3,000 1-napthylisocyanate 1 704 1.2 200 1.9 493 9.1 6 none 1 1,600 phenyl isocyanate 1165 0.3 126 1.2 62 1.1 7 none 1 1,600 4,4′-MDI 2 298 0.5 506 4.7 320 5.9

The foregoing examples of the present invention are offered for thepurpose of illustration and not limitation. It will be apparent to thoseskilled in the art that the embodiments described herein may be modifiedor revised in various ways without departing from the spirit and scopeof the invention. The scope of the invention is to be measured by theappended claims.

What is claimed is:
 1. A process for marking one of a fluid, a fluidblend or a solid composition, the process comprising adding to the oneof a fluid, a fluid blend or a solid the reaction product of: at leastone fluorophore-containing reactive polymer, said reactive polymer beingprepared from monomers having no more than one 1,2-epoxide group permolecule, having a molecular weight in the range of 250 to 40,000 Da,and having from 1 to 8 active hydrogen atoms per molecule of reactivepolymer, wherein said reactive polymer is chosen from polyesters andpolyether polyols, and optionally containing a polyamine unit of theformula NCH₂CH₂N; and at least one unsubstituted or substituted arylisocyanate or an unsubstituted aliphatic or cycloaliphatic isocyanate,wherein said unsubstituted aliphatic or cycloaliphatic isocyanate isselected from the group consisting of 1,6-hexamethylene-diisocyanate,isophorone diisocyanate, 2,4- and 2,6-hexahydrotoluene-diisocyanate andisomeric mixtures thereof, 4,4′-, 2,2′- and2,4′-dicyclohexylmethanediisocyanate and 1,3-tetramethylene xylenediisocyanate; at an isocyanate index of about 100 or less, wherein thereaction product emits fluorescence in the ultraviolet (UV), visible, ornear infrared (IR) region.
 2. The process according to claim 1, whereinthe fluorophore of the fluorophore-containing reactive polymer is chosenfrom nonylphenol and Bisphenol A.
 3. The process according to claim 1,wherein the reactive polymer has a molecular weight of about 500 toabout 20,000 Da.
 4. The process according to claim 1, wherein theunsubstituted or substituted aryl isocyanate is chosen from4,4′-diphenylmethane diisocyanate (MDI), polymeric MDI, toluenediisocyanate, allophanate-modified isocyanates, phenyl isocyanate,naphthalene isocyanate, naphthalene diisocyanate, isocyanate-terminatedprepolymers and carbodiimide-modified isocyanates.
 5. The processaccording to claim 1, wherein the reaction product has an excitationwavelength to induce fluorescence of greater than about 210 nm and anemission wavelength of greater than about 290 nm.
 6. The processaccording to claim 1, wherein the reaction product has a molecularweight greater than about 300 Da.
 7. The process according to claim 1,wherein the reaction product has a molecular weight of from about 1,000Da to about 50,000 Da.
 8. The process according to claim 1, wherein thefluid blend is chosen from diesel fuel, gasoline and heating oil.
 9. Theprocess of claim 1, wherein said polyether polyols are prepared from oneor more alkylene oxides comprising ethylene oxide, propylene oxide,butylene oxides, and combinations thereof.